This invention relates to a vibration reducing device for bicycles, particularly to one designed to be provided with a progressive vibration-absorbing structure.
A conventional vibration reducing device for bicycles may be a front-mounted vibration reducing device or a rear-mounted vibration reducing device. The front-mounted device is located at a front fork. The rear-mounted device is located almost horizontally between a seat stay A and a crosswise tube B, as shown in FIG. 1.
It is well known that a conventional vibration reducing device, whether front-mounted or rear-mounted, includes a vibration absorbing element such as a spiral spring, and an oil pressure guide rod provided in the axial direction. The rear-mounted vibration device is quite susceptible to damage, due to the seat stay contacting the rear-mounted vibration reducing device and non-axial compression causing bending or breaking of the oil pressure guide rod or oil leakage from the oil pressure cylinder.
Further, a bicycle equipped with a vibration reducing device may be used on rough, uneven ground so that the oil pressure cylinder for the oil pressure guide rod of the front-mounted vibration reducing device may be easily damaged.
Further, the tendency toward designing a bicycle of light weight may weaken a traditional vibration reducing device.
The present invention has been devised to offer a vibration reducing device for bicycles using a sulfurized synthetic rubber shrinkable knotted tube as a vibration absorbing element. The synthetic rubber shrinkable knotted tube is provided with at least one spherical knot, and with a net reinforcing layer contained in the tube wall to add strength and resilience to the shrinkable knotted tube
A feature of the invention is the synthetic rubber vibration knotted tube provided with one or more knots that function as shrinking and lengthening elements. The tube is filled with air for adjusting elastic response to vibration.
Another feature of the invention is the synthetic rubber shrinkable knotted tube provided with two spherical knots with different thicknesses or with different outer diameters.
One more feature of the invention is that the synthetic rubber shrinkable knotted tube is made of a material with an excellent elastic property, so that it will not break or split.